The present invention relates to brake actuating systems generally, and more particularly to a diaphragm-type pneumatic brake actuator having a closing valve.
It has long been recognized that when wheels for a vehicle skid during a sudden stop, the operator of the vehicle can lose much control. To prevent this, computerized anti-lock braking systems have been developed and are provided as optional or standard equipment on commercially available vehicles. These anti-lock braking systems sense when one or more of the wheels starts slowing down too rapidly, which indicates that the wheels are about to lock up and cause skid resulting in loss of operator control. Responsive to this sensed condition, the computerized anti-lock braking system controls the braking force, through hydraulic fluid or air pressure, to prevent the wheel(s) from locking up and to ensure maximum traction and control for a safe, controlled stop.
Although anti-lock brake systems prevent wheel lock-up and, thus, skidding, they generally do not compensate for other types of brake failure. For example, they do not resolve the problem of diaphragm rupture in a diaphragm-type pneumatic brake actuator which in addition to causing braking capacity loss for the wheel associated with the damaged actuator, can result in the loss of braking capacity for other wheels of the vehicle. That is, when the diaphragm in a diaphragm-type pneumatic brake actuator ruptures, pressurized air rushes through the resultant opening. This can lower the air pressure in the air pressure supply line coupled to the damaged actuator to the extent that another air brake actuator also supplied by that line is rendered nonfunctional.